The length of time for which the holding should last came to be specified, at first for a term of years and then for life, and some payment to the grantor was provided for, not pretending to represent the economic value of the land, but only to serve as a mark of his continued ownership.
This is actually the case; the Carboniferous, Cretaceous and Jurassic systems (qq.v.) contain coal-bearing strata though in unequal degrees,- the first being known as the Coal Measures proper, while the others are of small economic value in Great Britain, though more productive in workable coals on the continent of Europe.
Deposits of brown iron ore of great economic value occur in many sedimentary rocks, such as the Lias, Oolites and Lower Greensand of various parts of England.
Phosphorite, when occurring in large deposits, is a mineral of much economic value for conversion into the superphosphate largely used as a fertilizing agent.
The pine and hardwood forests are of great economic value because of the density of their growth, and there are at hand the means of profitable development of this industry in the numerous watercourses which make logging cheap and expeditious.
Flora and Faunx.-Although the vegetation of the Nicobars has received much desultory attention from scientific observers, it has not been subjected to a systematic examination by the Indian Forest Department like that of the Andamans, and indeed the forests are quite inferior in economic value to those of the more northerly group; besides fruit trees - such as the coco-nut (Cocos nucifera), the betel-nut (Areca catechu), and the mellori (Pandanus leeram) - a thatching palm (Nipa fruticans) and various timber trees have some commercial value, but only one timber tree (Myristica irya)would be considered first-class in the Andamans.
The kinds of greatest economic value are sturgeon, shad, salmon, lampreys, eels, pike and whiting.
There are many short streams along this coast, fed by heavy rainfalls, but they have no geographic importance and no economic value under existing conditions.
Per thousand, so that the economic value of using it in admixture with coal gas and then enriching the mixture by any cheap carburetting process is manifest.
The outer layer of bark in the cork oak by annual additions from within gradually becomes a thick soft homogeneous mass, possessing those compressible and elastic properties upon which the economic value of the material chiefly depends.